DE 24 42 397 A1 discloses such a cap for a temperature-dependent switch, which cap is designed as a cup-shaped surrounding housing which can be pushed from below with fit onto the switch such that strands welded to the upper part of the switch housing lead out of the cap. The upper opening of the cap is thereafter closed by a resin covering.
Such temperature-dependent switches are widely known from the prior art. They are used to protect electrical devices, for example hairdryers, motors of lye pumps, irons etc., from overheating and/or an excessively high current.
For this purpose, the known temperature-dependent switches are electrically connected in series with the device to be protected in the supply circuit of the latter, with the result that the operating current of the device to be protected flows through the temperature-dependent switch. The switch is also fitted to the device to be protected in such a manner that it assumes the temperature of the device to be protected, for which purpose the switch is ideally provided with a heat transfer area which lies on the electrical device to be protected.
The known temperature-dependent switches comprise a temperature-dependent switching mechanism which, on the basis of its temperature, opens or closes an electrical connection between two connection areas provided on the outer surface of the housing of the switch. For this purpose, a bimetal part is generally provided in the switching mechanism, which part, upon reaching its switching temperature, is abruptly deformed from its low-temperature position into its high-temperature position and in the process generally lifts a movable contact part off a fixed contact part.
The fixed contact part is connected to one of the two connection areas, whereas the movable contact part is connected to the second connection area either via the bimetal part or via a snap-action disk or spring assigned to the bimetal part.
Designs in which the bimetal part carries a contact bridge which directly establishes an electrical connection between two connection areas are also known.
Examples of such temperature-dependent switches are described in DE 21 21 802 A, DE 26 44 411 A, DE 196 23 570, DE 103 01 803 and further intellectual property rights of this applicant, reference being made to these intellectual property rights regarding further details of the design of such temperature dependent switches.
In addition to the thermal coupling of the known switches, it is also necessary to ensure that the switches are electrically insulated from the electrical device to be protected so that undesirable short circuits do not occur.
This is because the known switches often have an electrically conductive housing lower part which is in the form of a pot and accommodates the temperature-dependent switching mechanism. The electrically conductive housing lower part is closed by a cover part which is likewise electrically conductive and is fixed to the housing lower part with the interposition of an insulating film. The first connection area is provided on the cover part, whereas the second connection area is provided on the base, the side wall or the rim of the housing lower part which holds the cover part.
Leads, generally either flexible connection strands or rigid connection lugs, are now electrically connected, generally soldered or welded, to these two connection areas, the strands or connection lugs then being used to further connect the known temperature-dependent switches.
The prefabricated switches provided with strands or connection lugs in this manner are then provided with a cap in order to electrically insulate the switches with respect to the outside. If the switches are provided with connection lugs, the caps have corresponding slots through which the connection lugs have to be threaded when pushing the cap onto the switch, which is not only correspondingly time-consuming and arduous but also always entails the risk of the electrical connection between the connection lugs and the connection areas being damaged or the connection lugs bending, with the result that they are not suitable for subsequent automatic installation in electrical devices to be protected but rather have to be reworked.
In contrast, if the leads are in the form of strands, the switches are provided with so-called shrink-fitted caps which are closed at one end, with the result that, after the shrink-fitted caps have been pushed onto the switches prefabricated with the strands, the strands at the other end project from the shrink-fitted cap. The shrink-fitted caps are then shrunk onto the switch.
One example of such a shrink-fitted cap is shown in DE 197 05 153 A1, DE 197 54 158 A1 showing a method for closing such a shrink-fitted cap after the switch with soldered strands has been inserted.
Switches which are provided with a cap or an insertion or surrounding housing are disclosed, for example, in DE 92 14 543 U, DE 91 02 841 U, DE 197 05 441 A1, DE 195 45 996 A1 or DE 10 205 001 371 A1.
All of these known caps for temperature-dependent switches have the disadvantage that the caps or surrounding housings either have a very complicated design or else the mounting of the cap on the switch which has already been provided with connection lugs is complicated and cannot be automated.